This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A098035 #18 Jun 06 2025 08:34:31
%S A098035 -1,-2,-1,-3,0,-3,-1,-3,0,-2,-1,-5,0,-1,0,-4,-1,-3,-1,-2,0,-3,-1,-5,1,
%T A098035 -1,0,-3,-2,-4,-1,-3,0,-1,0,-6,0,-1,0,-3,-2,-2,-1,-4,2,-3,-1,-6,-1,0,
%U A098035 -1,-3,-1,-2,0,-2,0,-4,-1,-6,0,-2,1,-2,0,-4,-1,-1,-2,-2,-1,-7,0,-1,1,-1,-2,-3,-1,-4,1,-4,-1,-4,1,-1,-2,-5,-1,-2,0,-3,0,-1
%N A098035 a(n) = Sum_{d|n} mu(d+1), where mu() is the Moebius function.
%H A098035 R. J. Mathar, <a href="/A098035/b098035.txt">Table of n, a(n) for n = 1..10000</a>
%e A098035 The divisors of 12 are 1, 2, 3, 4, 6 and 12. So a(12) = mu(2) + mu(3) + mu(4) + mu(5) + mu(7) + mu(13) = -1 - 1 + 0 - 1 - 1 - 1 = -5.
%t A098035 a[n_] := Plus @@ MoebiusMu[Divisors[n] + 1]; Table[ a[n], {n, 105}] (* _Robert G. Wilson v_, Nov 01 2004 *)
%o A098035 (PARI) a(n) = sumdiv(n, d, moebius(d+1)); \\ _Amiram Eldar_, Jun 06 2025
%Y A098035 Cf. A008683, A098018.
%K A098035 sign
%O A098035 1,2
%A A098035 _Leroy Quet_, Oct 24 2004
%E A098035 More terms from _Robert G. Wilson v_, Nov 01 2004